For millions of breast cancer survivors and menopausal women without breast cancer, hot flashes are frequent, severe, and bothersome events that can interfere with daily life and negatively influence mood, affect, and/or sleep. Unfortunately, the scientific basis for managing hot flashes is limited. The major conclusion from a recent National Institutes of Health state-of-the-science conference was that additional data are needed on the efficacy and appropriateness of non-hormonal hot flash treatments. Although slow deep breathing has been recommended by the North American Menopause Society as a first-line treatment for hot flashes, these recommendations are based on two previous studies that included small numbers of menopausal women without breast cancer, used a complex time- and resource-intensive instructional protocol, and incorporated a narrow range of outcomes. These limitations restrict current evidence for efficacy and reduce the likelihood that this promising non-hormonal hot flash treatment can be disseminated into widespread use. The proposed randomized, controlled trial evaluates a simplified DVD-based at-home slow deep breathing training and practice program against a DVD-based attention control condition of fast shallow breathing training and a no-treatment usual care control condition among breast cancer survivors and menopausal women without breast cancer. Aims are to evaluate (1) efficacy for physiologic and subjective hot flashes (objective frequency and subjective frequency, severity, bother, duration), (2) efficacy for perceived hot flash interference and associated outcomes (mood, affect, sleep), (3) differences in efficacy between breast cancer survivors and menopausal women without cancer, and (4) acceptability and usability in anticipation of disseminating findings into clinical practice (treatment acceptability, outcome expectancy, treatment credibility, and frequency of practice and application). This study will also examine baseline characteristics as potential covariates of efficacy, including objective hot flash frequency, body mass index, race, ethnicity, education, prior breath training, smoking status, menopausal status, use of selective estrogen receptor modulators or aromatase inhibitors, use of other hot flash treatments, and comorbidities. 195 breast cancer survivors and 195 menopausal women without cancer who meet inclusion criteria will be stratified and randomized to slow deep breathing, an attention control condition of fast shallow breathing, or a no-treatment usual care control group. Outcomes will be assessed at baseline and 8 and 16 weeks post-intervention by research assistants masked to randomization group. To assess treatment integrity among the slow deep breathing group, a portable respiratory transducer will be used at each data collection point to evaluate breathing depth and rate during normal breathing and slow deep breathing. Findings will provide empirical evidence for or against the use of slow deep breathing for relieving physiologic and/or subjective hot flashes, perceived hot flash interference and associated outcomes. Importantly, positive or negative findings will provide guidance for clinicians'recommendations and consumers'treatment selections either in favor of, or against, the use of slow deep breathing. If study results support efficacy, acceptability, and usability, our DVD-based intervention could be easily and widely disseminated for use in lieu of, or in addition to, existing pharmacologic or non-pharmacologic hot flash treatments. Public Health Relevance Paragraph: Findings from this study will provide empirical evidence for or against the use of slow deep breathing for relieving physiologic and/or subjective hot flashes, perceived hot flash interference and associated outcomes including mood, affect, and sleep. Findings will have relevance to clinicians and the millions of breast cancer survivors and menopausal women without breast cancer who are seeking proven and acceptable non- hormonal treatments for frequent, severe, and/or bothersome hot flashes.